Housing for an air handling unit and method of manufacture thereof

ABSTRACT

The invention relates to an air handling unit comprising a housing defining an interior space and a heat exchange element located within the interior space. The housing is provided with an air inlet and an air outlet communicating an exterior of the housing with the interior space. According to the invention the housing is at least partially formed from plastics material using a rotomoulding technique.

The invention relates to a three-dimensional plastic housing or a partthereof for an air handling unit, for instance a heating device, acooling device, a drying device, a humidifying device, anair-conditioner or the like. It further relates to method formanufacturing such a housing.

According to a known method the housing, optionally in components, ismanufactured by making use of an injection moulding technique.

It is known from the injection moulding art that the products formedtherewith are always subject to certain internal stresses. As result ofthe internal stresses, the impact resistance of the products in questionleaves something to be desired. It is moreover never wholly possible toavoid the formed products having a seam.

A further drawback of the injection moulding art is that the manufactureof larger products is problematic. This is particularly a result ofrelatively high mould costs, which of course result in high productcosts.

According to the present invention, there is provided an air handlingunit comprising a housing defining an interior space and a heat exchangeelement located within the interior space, the housing being providedwith an air inlet and an air outlet communicating an exterior of thehousing with the interior space, wherein the housing is at leastpartially formed from plastics material using a rotomoulding technique.It has been found that by using a rotomoulding technique according tothe present invention, an improved stress free and substantiallyseamless product can be achieved. This is in particular desirable forlarge housings of more than 15,000 litres where the cost of injectionmoulding would be very high, in particular when the number of itemsproduced is low.

The invention also provides a method for manufacturing athree-dimensional plastic housing or a part thereof for an air handlingunit, for instance a heating device, a cooling device, a drying device,a humidifying device, an air-conditioner or the like, wherein thehousing is manufactured by rotomoulding in a mould to form asubstantially hollow body.

A particularly advantageous form of rotomoulding comprises:

(a) designing the external form of the housing, optionally subdividedinto its constituent parts;

(b) manufacturing a mould with a mould cavity having a formcorresponding with said external form, respectively optionally more thanone mould, which mould cavity is accessible for admitting plastic andcan subsequently be closed, which mould consists of at least two partssuch that the parts of the mould cavity bounded by these mould parts areall releasing;

(c) admitting into the mould cavity a limited quantity of plastic whichhas been plasticized in advance by heating and/or is plasticized on theheated wall of the mould cavity, which said limited quantity issufficient to form a wall having at least approximately a chosenthickness;

(d) closing and then setting the mould into a rotating movement,optionally about more than one axis of rotation;

(e) cooling the wall of the mould cavity during said rotating movement,whereby the plastic plasticized by heating also solidifies on this wallthrough cooling and thus forms a layer of cured plastic graduallybecoming thicker until all plastic introduced into the mould cavity hascured to form the housing for manufacturing, respectively a partthereof;

(f) opening the mould; and

(g) taking out the finished housing respectively a part thereof.

The housings, respectively their components, obtained with the methodaccording to the invention are seamless and free of stress, wherebytheir impact resistance is very good.

The invention further provides a great variety of possible dimensions.Effective housing volumes of 1 litre to more than 15,000 litres can forinstance be envisaged.

A great freedom of form and low investment costs are further realized.It is also easily possible to manufacture a plurality of colours withinsmall series, since all the plastic introduced into the mould is afterall converted without loss into finished product. In addition, thestated housings can be readily processed or post-processed.

The obtained products can advantageously be given a double-walled form,whereby the outside obtains an aesthetically attractive appearance,while the inside can be formed for technical purposes. Diversecomponents, such as a fan, a heat exchanger, a dewpoint cooler,electronic components or the like, can hereby be readily accommodated.Compared to the described prior art, the invention can thus result in areduction in cost because fewer shell parts or filler pieces have to bemanufactured in order to realize all required functions. This latteraspect also saves working time in processing or assembly, while theextra steps required according to the prior art can moreover be omitted,which reduces errors and losses.

In the case of a double-walled housing, the hollow space available inthe housing can be used as air duct, for instance to draw in outside airto a fan. Pipes, cables and hoses can also be accommodated in the spacein question. Colours as well as wall thicknesses can easily be chosenand changed or optimized.

In order to optimize the housing at the design stage, use can be made ofa method of the described type, comprising the step of

(h) successively applying the method according to claim 1 at the designstage, wherein during step (c) different quantities of plastic areadmitted each time into the mould cavity; and

(i) technically evaluating the thus obtained housings and choosing thebest in accordance with chosen criteria for the definitive seriesproduction.

In a specific embodiment the method according to the invention isapplied, comprising the step of

(j) performing step (c) with PP, PA, PE, and in particular LLDPE, asplastic.

The invention also relates to a three-dimensional plastic housing for anair handling unit, for instance a heating device, a cooling device, adrying device, a humidifying device, an air-conditioner or the like,manufactured by applying the method according to the above statedspecifications.

An embodiments of the invention will now be explained in further detailby way of example only with reference to the accompanying figures, inwhich:

FIG. 1 shows a perspective view of one side of a housing that has beencut in half, wherein for the sake of clarity the components to beaccommodated therein are drawn in exploded view;

FIG. 2 shows a similar view to FIG. 1 wherein the components areaccommodated within the housing; and

FIG. 3 is a perspective view from the other side in the assembledsituation according to FIG. 2.

FIG. 1 shows an housing 1 comprising a bottom 2 and a cover 3 which isconnected thereto by means of suitable means, for instance screwconnections, snap connections or the like. Both the bottom 2 and cover 3are formed by rotomoulding and comprise interior cavities. A heatexchanger 4 is located within an interior space formed within thehousing 1. The heat exchanger is preferably a dewpoint cooler, i.e. adevice able to cool air substantially through use of the heat releasedduring the evaporation of water. In a dewpoint cooler, a stream of airafter passing over a first dry side of a heat exchange element issubsequently split into two separate flows. A first part of the flow isoutput to the space where cooling is required. The second part of theflow is returned over a second moist or wet side of the heat exchangerwhere it absorbs moisture by evaporation from the surface of the heatexchanger into the airflow. The second part of the flow is maintainedseparate from the first part of the flow and subsequently exhausted tothe environment.

For driving the air flow, use is made of a fan 5 (see also FIG. 2)which, according to FIG. 1, comprises among others the followingcomponents: a rotor 6 with blades 7, two frame plates 8, 9 with spacers10 and stator rings 11, 12. Further accommodated in housing 1 are forinstance control elements such as electronic units and air filters 13,14. Reference is also made in this respect to FIG. 2.

During installation of the components in the housing, further openingsmay be formed into the hollow cavities of both the bottom 2 and thecover 3. These openings may serve as inlet or outlet openings to theinterior of the housing or may serve to install components or wiringetc. within the cavities of the bottom 2 or cover 3. FIG. 2 shows e.g. awater tank 18 located within the cavity of the bottom 2. Furthermore,air filters 13, 14 can be partially located within an opening (notshown) formed in the bottom 2. FIG. 2 also shows clearly the manner inwhich the airflow generated by fan 5 can be discharged to the outsidethrough the heat exchanger 4 according to an arrow 15 via an air outlet16. The air inlet to the fan 5 may be provided by an opening 19 formedin the bottom 2.

FIG. 2 and 3 each show one side of a half of a finished air handlingunit 17.

1. An air handling unit comprising a housing defining an interior spaceand a heat exchange element located within the interior space, thehousing being provided with an air inlet and an air outlet communicatingan exterior of the housing with the interior space, wherein the housingis at least partially formed from plastics material using a rotomouldingtechnique.
 2. The air handling unit according to claim 1, wherein theheat exchange element is an evaporative heat exchanger.
 3. The airhandling unit according to claim 1 or claim 2 wherein the housing isprovided with at least two air outlets for the separate output of twoseparate air streams from the heat exchange element.
 4. The air handlingunit according to any preceding claim, wherein the housing is formed ofa first housing part and a second housing part, which interact to definethe interior space and wherein at least the first housing part is formedby rotomoulding.
 5. The air handling unit according to claim 4, whereinthe first housing part comprises a cavity.
 6. The air handling unitaccording to claim 5, further comprising an additional component atleast partially located within the cavity of the first housing part. 7.The air handling unit according to claim 6, wherein the additionalcomponent is a water reservoir.
 8. A method for manufacturing athree-dimensional plastic housing or a part thereof for an air handlingunit, for instance a heating device, a cooling device, a drying device,a humidifying device, an air-conditioner or the like, wherein thehousing is manufactured by rotomoulding in a mould to form asubstantially hollow body.
 9. The method according to claim 8comprising: (a) designing the external form of the housing, optionallysubdivided into its constituent parts; (b) manufacturing a mould with amould cavity having a form corresponding with said external form,respectively optionally more than one mould, the mould cavity beingaccessible for admitting plastic and being subsequently closeable; (c)admitting into the mould cavity a limited quantity of plastic which hasbeen plasticized in advance by heating and/or is plasticized on theheated wall of the mould cavity, the limited quantity being sufficientto form a wall having a chosen thickness; (d) closing the mould; (e)setting the mould into a rotating movement, optionally about more thanone axis of rotation; (f) cooling a wall of the mould cavity whilecontinuing the rotating movement, whereby the plastic plasticized byheating solidifies on the mould wall through cooling and thus forms alayer of cured plastic gradually becoming thicker until substantiallyall plastic introduced into the mould cavity has cured to form thehousing for manufacturing, respectively a part thereof; (g) opening themould; and (h) taking out the finished housing respectively a partthereof.
 10. The method as claimed in claim 9, further comprising: (i)successively applying the method according to claim 1 at the designstage, wherein during step (c) different quantities of plastic areadmitted each time into the mould cavity; and (j) technically evaluatingthe thus obtained housings and choosing the best in accordance withchosen criteria for the definitive series production.
 11. The method asclaimed in claim 9, comprising: (k) performing step (c) with PP, PA, PE,or in particular LLDPE, as plastic.
 12. A housing for an air handlingunit, for instance a heating device, a cooling device, a drying device,a humidifying device, an air-conditioner or the like, manufacturedaccording to the method as claimed in any of claims 9 to
 11. 13. Ahousing as defined in any of claims 1 to 8 or 12 wherein the volume ofthe housing is more than 15 000 litres.